1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a method for manufacturing the same.
2. Background of the Related Art
In general, a Cathode Ray Tube (CRT), one of display devices, has been widely used for monitors of information terminals and measuring instruments including a television. However, it was difficult for the CRT to actively adapt to miniaturization and lightweight due to its weight and size.
A Liquid Crystal Display (LCD) device having a thin and small size has been actively developed in order to substitute for such a CRT. Recently, the LCD device is used as a flat panel display device. Thus, a demand of the LCD device is increasing consistently.
Such an LCD device is largely classified into a transmissive LCD device and a reflective LCD device according to a light source. The transmissive LCD device using a back light as the light source can obtain a luminous picture in the dark outside. However, the transmissive LCD device has large size and bulk, and high power consumption due to the back light. The reflective LCD device does not use the back light, thereby obtaining low power consumption, small size and bulk. However, there is a limitation that the reflective LCD device cannot be used in the dark outside.
To solve these problems, a transflective LCD device is disclosed, which can be used as the reflective LCD device or the transmissive LCD device at need.
FIG. 1a and FIG. 1b are plan views of the transflective LCD device according to a related art. As shown in FIG. 1a, a reflective electrode 3 is formed in a pixel region, and then a hole pattern 4 is formed in the reflective electrode 3. In this structure, light partially passes through the hole pattern 4. Or, as shown in FIG. 1b, the reflective electrode 3 is formed at a predetermined portion of the pixel region, and then a transparent electrode 5 is formed in the rest of the pixel region.
Although not described, “1” is a gate line, and “2” is a data line.
A related art LCD device will be described with reference to the accompanying drawings.
FIG. 2 is a sectional view of the related art LCD device. In FIG. 2, the LCD device includes an insulating substrate 11, a gate electrode 13 and a first electrode 13a of a storage capacitor, a gate insulating film 15, a semiconductor film 17 and source/drain electrodes 19 and 19a, a second electrode 19b of the storage capacitor, a first passivation film 21, a reflective electrode 23, a second passivation film 25, and a transparent electrode 29. At this time, the gate electrode 13 and the first electrode 13a of the storage capacitor are formed on the insulating substrate 11. The gate insulating film 15 is formed on the insulating substrate 11 including the gate electrode 13, and then the semiconductor film 17, source/drain electrodes 19 and 19a, and the second electrode 19b of the storage capacitor are formed on the gate insulating film 15. Subsequently, the first passivation film 21 is formed on an entire surface of the gate insulating film 15 including the second electrode 19b, and the reflective electrode 23 is formed on the first passivation film 21. The second passivation film 25 is formed on an entire surface of the first passivation film 21 including the reflective electrode 23. Then, the transparent electrode 29 is connected with the reflective electrode 23 through the second passivation film 25, and is connected with the drain electrode 19a and the second electrode 19b of the storage capacitor through the second passivation film 25 and the first passivation film 21.
A method for manufacturing the LCD device having such structure will be described with reference to FIG. 3a to FIG. 3e. 
For reference, a TFT region (I) and a storage region (II) are simultaneously shown in the drawings.
As shown in FIG. 3a, a metal film using Al, Ta, MO or Al alloy is formed on the insulating substrate 11 by sputtering, and is patterned by photolithography, so that the gate electrode 13 is formed in the TFT region (I), and the first electrode 13a of the storage capacitor is formed in the storage region (II). Then, the gate insulating film 15 is formed on the entire surface of the insulating substrate 11 including the gate electrode 13 by chemical vapor deposition (CVD). At this time, the gate insulating film 15 is generally formed of silicon nitride (SiNx) or silicon oxide (SiOx). Although not shown, a gate pad is formed to have some distances with the first electrode 13a of the storage capacitor.
As shown in FIG. 3b, the semiconductor film is formed on the gate insulating film 15 by sputtering, and then is patterned by photolithography, so that the semiconductor film 17 is formed on the gate insulating film 15 above the gate electrode 13. Then, the metal film is formed on the entire surface of the gate insulating film 15 including the semiconductor film 17 by sputtering. Subsequently, source/drain electrodes 19 and 19a are divided on the semiconductor film 17 by photolithography, and the second electrode 19b of the storage capacitor is formed. Although not shown, a data pad is formed on the gate insulating film 15 to have some distances with the second electrode 19b of the storage capacitor.
As shown in FIG. 3c, the first passivation film 21 is formed on the entire surface of the gate insulating film 15 including the second electrode 19b of the storage capacitor by CVD. Then, an aluminum film is formed on the first passivation film 21 by sputtering, and is patterned, thereby forming the reflective electrode 23 on the predetermined portion of the passivation film 21. The second passivation film 25 is formed on the entire surface of the first passivation film 21 including the reflective electrode 23 by CVD.
As shown in FIG. 3d, the first and second passivation films 21 and 25 are selectively removed to expose the surfaces of the drain electrode 19a, the reflective electrode 23 and the second electrode 19b of the storage capacitor, thereby forming contact holes 27a, 27b and 27c. 
As shown in FIG. 3e, an indium tin oxide (ITO) film is formed on the surface of the second passivation film 25 including the contact holes 27a, 27b and 27c. Then, the transparent electrode 29 is formed to be electrically connected with the second electrode 19b of the storage capacitor and the reflective electrode 23.
Although not shown, a liquid crystal layer is formed between the insulating substrate 11 and an opposing substrate (not shown), so that manufacturing process steps are completed.
However, the related art LCD device has the following problems.
If the reflective electrode of aluminum is contacted with the transparent electrode of ITO, oxygen of ITO reacts with aluminum. Therefore, an undesired insulating film (Al2O3) is formed at an interface between the reflective and transparent electrodes 23 and 29. That is, an ohmic contact is remarkably increased in this portion, and then a driving voltage is not uniformly provided to the ITO and the reflective electrode. Accordingly, a parasitic capacitor is formed due to the insulating film formed between the reflective electrode and ITO, thereby resulting in a charged voltage negatively affecting the operation of pixels.